Digital-analogue converter



Nov. 29, 1966 AKIRA SHIIKI 3,288,365

DIGITAL-ANALOGUE CONVERTER Filed June 50, 1965 2 Sheets-Sheet 1 ,NZO

I NVEN TOR. AKIRA SHIIKI ATTORNEY Nov. 29, 1966 AKIRA SHllKl DIGITAL-ANALOGUE CONVERTER 2 Sheets-Sheet 2 Filed June 50, 1965 TIME TIME

INVENTOR.

' AKIRA SHIIKI ATTORNEY United States Patent() 3,288,365 DIGITAL-ANALOGUE CONVERTER Akira Shiiki, Tokyo, Japan, assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed June 30, 1965, Ser. No. 468,382 Claims priority, application Japan, June 30, 1964, 39/ 37,187 2 Claims. (Cl. 235-201) This invention relates to a D-A converter used in an automatic control system to convert a signal obtained by a digital device to an analogue and more particularly to a D-A converter which uses a bias action of a control fluid stream jetted from a nozzle, senses an air pulse as an input and supplies air pressure in analogue as an output. Therefore, there is almost no mechanical operating parts in the D-A converter, which operates in precise and in almost no accident in response to fluid ope-ration.

The object and nature of the present invention will be illustrated in conjunction with the attached drawings.

FIG. 1 is a fragmental-sectional elevation of an embodiment of D-A converter provided in accordance with the present invention,

FIG. 2 is curves showing the relation between the flow of an input pulse and the time, and

FIG. 3 is curves showing the relation between the internal pressure of a tank and the time.

Referring to FIG. 1, a is a base plate provided with punched fluid channels thereon and the base plate a is sandwiched at the both side surfaces thereof by two cover plates 12, 23 are holding screws used for the said sandwich construction. The resistances of restriction valves 2, 12, 14 and 16 are R R R and R respectively. 10 and 11 are supply inlets of the actuating air, and 9 is a jet nozzle. 8 is an inlet of an input air pulse. Inlet 8 is connected to a pressure chamber 22 and a control gate 7 opened to a jet outlet of jet nozzle 9. 3 and 4 are branch channels, one channel 3 of which being connected to a tank 17 and the other channel 4 of which being connected through an exhaust outlet 1 to the atmosphere. A channel 13 is connected through restriction valve 14 to a connection gate 15 of a load. An exhaust outlet 19 of said tank is closed and opened under the control of a diaphragm 21. Furthermore, 18 and 20 are a spring and an air exhaust outlet, respectively.

In case of an input signal being zero, an air supplied from air supply inlet is jetted into a domain 6 by jet nozzle 9, and there being no supplement of the input signal air from control inlet 7, the domain 6 becomes decreased in pressure therein considerably by the fact that the domain is surrounded by the approached walls thereof and the air stream and no air is supplied from the external of said domain. Accordingly, the air stream is biased to flow into the left channel 4 and exhausted to the atmosphere from exhaust outlet 1.

Moreover, as the result of absence of the input signal, the internal pressure of a pressure chamber 22 is maintained at the atmosphere pressure and diaphragm 21 is depressed by spring 18 to make exhaust outlet 19 open. Therefore, the air from supply inlet 11 is exhausted through restriction valves 12 and 16, tank 17, exhaust outlet 19 and air exhaust outlet 20.

On the other hand, in case of input signal being supplied from input air pulse inlet 8, the supplied signal air operates to push up diaphragm 21 in pressure chamber 22 so as to close exhaust outlet 19, and at the same time the supplied signal air enters domain 6 from control gate 7 to bias the jet air stream to the right and then to guide the jet air stream through branch channel 3 and restriction valve 2 to tank 17. Moreover, the air supplied from supply inlet 11 also enters tank 17 to increase the internal pressure P thereof.

Supposing that the input signal has the rectangular wave form oscillating at frequency f as shown in FIG. 2, during the time t of the constant flow coming from control gate 7, supply inlets 10 and 11 enters together into tank 17 to increase the internal pressure P thereof. In other words,

P T- C t wherein, Q Q and Q are the constant flow' from control gate 7, supply inlets 10 and 11, respectively, and C is a capacity of tank 17; Q is in terms of mass flow rate,

while temperature and the equation constant are not considered for simplicity.

Furthermore it is noted that the input signal is z r during the time of Accordingly, in this duration air supplied from supply inlet 10 is exhausted from exhaust outlet 1-, and the air accumulated in tank 17 during the time of is also exhausted through exhaust outlet 19 from air exhaust outlet 20. Exhaust outlet 19 and air exhaust outlet 20 being small in exhausting resistance, the air accumulated in tank 17 will be exhausted instantaneously. Therefore, the internal pressure P in tank 17 becomes nearly zero (PEO) during the time of Accordingly, the variation of the internal pressure P to the time can be charted as FIG. 3.

Supposing the primary pressure at channel 13 where the air flows (represented by Q from supply inlet 11 passes through restriction valve 16 (having resistance R into tank 17 to be P the secondary pressure thereof will be P which is the internal pressure of tank 17, and the relation between the primary pressure P and the secondary pressure P can be expressed as follows:

l T+(Q8 4) The internal pressure P of tank 17 varies in saw waveform as shown in FIG. 3, so it will be seen that the primary pressure P at the channel 13 also varies in saw waveform. However, by having the primary pressure P passed through restriction valve 14 with a large resistance, the ripple of the primary pressure will be absorbed by restriction valve 14 and therefore a mean value P means of the primary pressure P will be supplied to a load connected to connection gate 15. The mean value P mean can be expressed as follows:

1 f P, mean=iL P dt Patented Nov. 29, 1966 P mean Q3 In accordance with the present invention, a D-A converter is provided with has little mechanical and electrical operating parts, performs D-A conversion operation easily and precisely only using of the stream operation of a fluid and operates in quiet and almost no accident for a long period maintaining the accuracy.

What I claim is:

1. A fluid operated digital to analogue converter comprising, a tank means including a first inlet means for receiving a first fluid stream, a second inlet means for receiving a second fluid stream and an exhaust means, a fluid amplifying means connected to said first tank inlet means and biased for diverting said first fluid stream therefrom, said tank exhaust means including a normally opened switching means through which said second fluid stream normally exhausts, said second tank inlet means passing through first and second restriction mean-s prior to entry into said tank, load connection means located between said first and second restriction means, and means for applying an input in the form of a pulsed fluid stream commonly to said fluid amplifying means and said switch ing means, whereby an input pulse from said pulsed fluid stream diverts said first fluid stream into said tank means and opera-bly closes said normally opened switching means within said tank exhaust means for increasing the pressure within said tank means and applying said pressure to said load connection means as an analogue output representation of said pulsed fluid stream input.

2. A fluid operated digital to analogue converter comprising, a tank including a first inlet for receiving a first fluid stream, a second inlet for receiving a second fluid stream, and an exhaust outlet, a fluid amplifier connected to said first tank inlet and biased for diverting said first fluid stream therefrom, a restrictive valve located within said connection between said fluid amplifier and said tank, a normally opened, spring biased, switching valve located within said tank exhaust outlet, means commonly connecting said fluid amplifier and said normally opened switching valve operative to apply a pulsed fluid stream input thereto for diverting said first fluid stream into said tank and for closing said switching valve, said second tank inlet passing through first and second restrictive valve means prior to entry int-o said tank, load connection means loacted between said first and second restrictive valve means, and a final restrictive valve located within said load connection means for forming a load channel therebetween, whereby an input pulse from said pulsed fluid stream diverts said first fluid stream into said tank and closes said switching valve thereby increasing the pressure Within said tank and consequently increasing the pressure within said load channel for providing an output pressure increase through said load final restrictive valve as an analogue representation of said pulsed fluid stream input.

References Cited by the Examiner UNITED STATES PATENTS 3,128,040 4/1964 Norwood 235-201 3,175,569 3/1965 Sowers 235-201 X 3,199,782 8/1965 Shinn 235201 3,221,990 12/1965 Warren 235201 RICHARD B. WILKINSON, Primary Examiner.

LOUIS I. CAPOZI, Examiner.

W. F. BAUER, Assistant Examiner. 

1. A FLUID OPERATED DIGITAL TO ANALOGUE CONVERTER COMPRISING, A TANK MEANS INCLUDING A FIRST INLET MEANS FOR RECEIVING A FIRST FLUID STREAM, A SECOND INLET MEANS FOR RECEIVING A SECOND FLUID STREAM AND AN EXHAUST MEANS, A FLUID AMPLIFYING MEANS CONNECTED TO SAID FIRST TANK INLET MEAN AND BIASED FOR DIVERTING SAID FIRST FLUID STREAM THEREFROM, SAID TANK EXHAUST MEANS INCLUDING A NORMALLY OPENED SWITCHING MEANS THROUGH WHICH SAID SECOND FLUID STREAM NORMALLY EXHAUSTS, SAID SECOND TANK INLET MEANS PASSING THROUGH FIRST AND SECOND RESTRICTION MEANS PRIOR TO ENTRY INTO SAID TANK, LOAD CONNECTION MEANS LOCATED BETWEEN SAID FIRST AND SECOND RESTRICTION MEANS, AND MEANS FOR APPLYING AN INPUT IN THE FORM OF A PULSED FLUID STREAM COMMONLY TO SAID FLUID AMPLIFYING MEANS AND SAID SWITCHING MEANS, WHEREBY AN INPUT PULSE FROM SAID PULSED FLUID STREAM DIVERTS SAID FIRST FLUID STREAM INTO SAID TANK MEANS AND OPERABLY CLOSES SAID NORMALLY OPENED SWITCHING MEANS WITHIN SAID TANK EXHAUST MEANS FOR INCREASING THE PRESSURE WITHIN SAID TANK MEANS AND APPLYING SAID PRESSURE TO SAID LOAD CONNECTION MEANS AS AN ANALOGUE OUTPUT REPRESENTATION OF SAID PULSED FLUID STREAM INPUT. 